HBASE-29074 Balancer conditionals should support meta table isolation #6722
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| /* | ||
| * Licensed to the Apache Software Foundation (ASF) under one | ||
| * or more contributor license agreements. See the NOTICE file | ||
| * distributed with this work for additional information | ||
| * regarding copyright ownership. The ASF licenses this file | ||
| * to you under the Apache License, Version 2.0 (the | ||
| * "License"); you may not use this file except in compliance | ||
| * with the License. You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
| package org.apache.hadoop.hbase.master.balancer; | ||
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| import org.apache.hadoop.hbase.client.RegionInfo; | ||
| import org.apache.yetus.audience.InterfaceAudience; | ||
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| @InterfaceAudience.Private | ||
| public final class MetaTableIsolationCandidateGenerator extends TableIsolationCandidateGenerator { | ||
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| MetaTableIsolationCandidateGenerator(BalancerConditionals balancerConditionals) { | ||
| super(balancerConditionals); | ||
| } | ||
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| @Override | ||
| boolean shouldBeIsolated(RegionInfo regionInfo) { | ||
| return regionInfo.isMetaRegion(); | ||
| } | ||
| } |
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| /* | ||
| * Licensed to the Apache Software Foundation (ASF) under one | ||
| * or more contributor license agreements. See the NOTICE file | ||
| * distributed with this work for additional information | ||
| * regarding copyright ownership. The ASF licenses this file | ||
| * to you under the Apache License, Version 2.0 (the | ||
| * "License"); you may not use this file except in compliance | ||
| * with the License. You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
| package org.apache.hadoop.hbase.master.balancer; | ||
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| import org.apache.hadoop.hbase.client.RegionInfo; | ||
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| /** | ||
| * If enabled, this class will help the balancer ensure that the meta table lives on its own | ||
| * RegionServer. Configure this via {@link BalancerConditionals#ISOLATE_META_TABLE_KEY} | ||
| */ | ||
| class MetaTableIsolationConditional extends TableIsolationConditional { | ||
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Contributor
Author
There was a problem hiding this comment. This implementation, and the MetaTableIsolationCandidateGenerator, are so lightweight because I anticipate adding a SystemTableIsolationConditional/CandidateGenerator soon |
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| public MetaTableIsolationConditional(BalancerConditionals balancerConditionals, | ||
| BalancerClusterState cluster) { | ||
| super(balancerConditionals, cluster); | ||
| } | ||
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| @Override | ||
| boolean isRegionToIsolate(RegionInfo regionInfo) { | ||
| return regionInfo.isMetaRegion(); | ||
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Member
There was a problem hiding this comment. Is it kind of a code smell that both the CandidateGenerator and the Conditional implementation have repeated logic? As you land your additional implementations, I wonder if this will suggest a change to the interfaces.
Contributor
Author
There was a problem hiding this comment. probably yes, let me think about reusability maybe. But I might chalk this up as a relatively small imperfection
Contributor
Author
There was a problem hiding this comment. I'm going to leave this alone for now, I think it's a disappointing but small reality of the logical divide between conditionals and candidate generators. Will keep thinking on this as I introduce the system table isolation conditional though |
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| } | ||
| } | ||
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| /* | ||
| * Licensed to the Apache Software Foundation (ASF) under one | ||
| * or more contributor license agreements. See the NOTICE file | ||
| * distributed with this work for additional information | ||
| * regarding copyright ownership. The ASF licenses this file | ||
| * to you under the Apache License, Version 2.0 (the | ||
| * "License"); you may not use this file except in compliance | ||
| * with the License. You may obtain a copy of the License at | ||
| * | ||
| * http://www.apache.org/licenses/LICENSE-2.0 | ||
| * | ||
| * Unless required by applicable law or agreed to in writing, software | ||
| * distributed under the License is distributed on an "AS IS" BASIS, | ||
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | ||
| * See the License for the specific language governing permissions and | ||
| * limitations under the License. | ||
| */ | ||
| package org.apache.hadoop.hbase.master.balancer; | ||
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| import java.util.ArrayList; | ||
| import java.util.HashSet; | ||
| import java.util.List; | ||
| import java.util.Set; | ||
| import org.apache.hadoop.hbase.client.RegionInfo; | ||
| import org.apache.yetus.audience.InterfaceAudience; | ||
| import org.slf4j.Logger; | ||
| import org.slf4j.LoggerFactory; | ||
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| @InterfaceAudience.Private | ||
| public abstract class TableIsolationCandidateGenerator | ||
| extends RegionPlanConditionalCandidateGenerator { | ||
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| private static final Logger LOG = LoggerFactory.getLogger(TableIsolationCandidateGenerator.class); | ||
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| TableIsolationCandidateGenerator(BalancerConditionals balancerConditionals) { | ||
| super(balancerConditionals); | ||
| } | ||
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| abstract boolean shouldBeIsolated(RegionInfo regionInfo); | ||
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| @Override | ||
| BalanceAction generate(BalancerClusterState cluster) { | ||
| return generateCandidate(cluster, false); | ||
| } | ||
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| BalanceAction generateCandidate(BalancerClusterState cluster, boolean isWeighing) { | ||
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Contributor
Author
There was a problem hiding this comment. This PR is pretty straightforward in my opinion; if there's any head scratching complexity, then it's in this method. I'm happy to explore breaking up this method, which is admittedly probably too long, but doing so would probably introduce a much larger diff because we'd need more objects to represent the state that should be passed around across the goals of isolation + colocation |
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| if (!getBalancerConditionals().isTableIsolationEnabled()) { | ||
| return BalanceAction.NULL_ACTION; | ||
| } | ||
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| List<MoveRegionAction> moves = new ArrayList<>(); | ||
| List<Integer> serverIndicesHoldingIsolatedRegions = new ArrayList<>(); | ||
| int isolatedTableMaxReplicaCount = 1; | ||
| for (int serverIdx : cluster.getShuffledServerIndices()) { | ||
| if (cluster.isStopRequested()) { | ||
| break; | ||
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Member
There was a problem hiding this comment. Should this return a NULL_ACTION instead of falling through to the rest of the method? ... this method is long enough that I cannot easily tell the nesting from cursory reading. Maybe the entirety of the remaining method body is inside this for-loop?
Contributor
Author
There was a problem hiding this comment. The method is definitely a little long; I talk about this a little bit here, but I'm basically on the fence about whether it's worth splitting this up Regarding whether this should return a null action, I'd say we should leave that to the logic at the end of this method which will submit any moves we have found, or return a null action if we haven't found any good moves |
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| } | ||
| boolean hasRegionsToIsolate = false; | ||
| Set<Integer> regionsToMove = new HashSet<>(); | ||
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| // Move non-target regions away from target regions, | ||
| // and track replica counts so we know how many isolated hosts we need | ||
| for (int regionIdx : cluster.regionsPerServer[serverIdx]) { | ||
| RegionInfo regionInfo = cluster.regions[regionIdx]; | ||
| if (shouldBeIsolated(regionInfo)) { | ||
| hasRegionsToIsolate = true; | ||
| int replicaCount = regionInfo.getReplicaId() + 1; | ||
| if (replicaCount > isolatedTableMaxReplicaCount) { | ||
| isolatedTableMaxReplicaCount = replicaCount; | ||
| } | ||
| } else { | ||
| regionsToMove.add(regionIdx); | ||
| } | ||
| } | ||
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| if (hasRegionsToIsolate) { | ||
| serverIndicesHoldingIsolatedRegions.add(serverIdx); | ||
| } | ||
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| // Generate non-system regions to move, if applicable | ||
| if (hasRegionsToIsolate && !regionsToMove.isEmpty()) { | ||
| for (int regionToMove : regionsToMove) { | ||
| for (int i = 0; i < cluster.numServers; i++) { | ||
| int targetServer = pickOtherRandomServer(cluster, serverIdx); | ||
| MoveRegionAction possibleMove = | ||
| new MoveRegionAction(regionToMove, serverIdx, targetServer); | ||
| if (!getBalancerConditionals().isViolating(cluster, possibleMove)) { | ||
| if (isWeighing) { | ||
| return possibleMove; | ||
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Member
There was a problem hiding this comment. Sorry, what does
Contributor
Author
There was a problem hiding this comment. Good question. So all candidate generators maintain a "weight" which influences their likelihood of being selected for the next proposed action. Conditional candidate generators, on brand with their binary decision making, are weighed based on whether they have any work to do — if they do, then we'll prioritize their moves over the more generic generators (like the |
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| } | ||
| cluster.doAction(possibleMove); // Update cluster state to reflect move | ||
| moves.add(possibleMove); | ||
| break; | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
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| // Try to consolidate regions on only n servers, where n is the number of replicas | ||
| if (serverIndicesHoldingIsolatedRegions.size() > isolatedTableMaxReplicaCount) { | ||
| // One target per replica | ||
| List<Integer> targetServerIndices = new ArrayList<>(); | ||
| for (int i = 0; i < isolatedTableMaxReplicaCount; i++) { | ||
| targetServerIndices.add(serverIndicesHoldingIsolatedRegions.get(i)); | ||
| } | ||
| // Move all isolated regions from non-targets to targets | ||
| for (int i = isolatedTableMaxReplicaCount; i | ||
| < serverIndicesHoldingIsolatedRegions.size(); i++) { | ||
| int fromServer = serverIndicesHoldingIsolatedRegions.get(i); | ||
| for (int regionIdx : cluster.regionsPerServer[fromServer]) { | ||
| RegionInfo regionInfo = cluster.regions[regionIdx]; | ||
| if (shouldBeIsolated(regionInfo)) { | ||
| int targetServer = targetServerIndices.get(i % isolatedTableMaxReplicaCount); | ||
| MoveRegionAction possibleMove = | ||
| new MoveRegionAction(regionIdx, fromServer, targetServer); | ||
| if (!getBalancerConditionals().isViolating(cluster, possibleMove)) { | ||
| if (isWeighing) { | ||
| return possibleMove; | ||
| } | ||
| cluster.doAction(possibleMove); // Update cluster state to reflect move | ||
| moves.add(possibleMove); | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
| return batchMovesAndResetClusterState(cluster, moves); | ||
| } | ||
| } | ||
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These logs are really noisy in tests, and low value imo, so I've demoted them to trace
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👍